Implantation bleeding?

So I had sex like the day after my period ended and then also the following week and the following week after that. The last time I had sex before my missed period I noticed some brownish pinkish discharge. I looked for advice and it said it may have been implantation bleeding as it occurred the week after my 'fertile window' ( I'm guessing that's when I conceived)But I am confused and kind of scared as I had sex the other day and had this same kind of thing. I asked a midwife and she said it's on to spot in early pregnancy after sex due to the cervix changing. Does this sound odd?